What are the peripheral smear findings in the workup of platelet disorders?

Answer

Careful examination of the peripheral smear is essential in a patient with thrombocytopenia.

Spurious thrombocytopenia due to platelet clumping or platelets adhering to neutrophils (platelet satellitism) can be seen on a smear (see image below).

Spurious thrombocytopenia. Peripheral smear of a patient reported to have platelet counts of 10,000-150,000/μL on various occasions. The smear shows clumping of the platelets and satellitism involving neutrophils and platelets.

Rare disorders, such as Bernard-Soulier syndrome, can be diagnosed based on the results from the peripheral smear (see image below). Careful examination of the smear is essential to exclude TTP and rare instances of acute leukemia presenting as thrombocytopenia.

Peripheral smear of a patient with Bernard-Soulier syndrome showing giant platelets. These platelets are not counted as platelets in most particle counters.

Spurious thrombocytopenia. Peripheral smear of a patient reported to have platelet counts of 10,000-150,000/μL on various occasions. The smear shows clumping of the platelets and satellitism involving neutrophils and platelets.

Examination of the peripheral smears in immune thrombocytopenic purpura often shows giant platelets. These platelets reflect the increased megakaryocytic mass in the marrow.

Peripheral smear of a patient with Bernard-Soulier syndrome showing giant platelets. These platelets are not counted as platelets in most particle counters.